The present invention generally relates to devices and methods useful in capturing embolic material during ablation of myocardial or vascular tissue. More specifically, the devices remove necrotic tissue debris generated during ablation of ectopic foci, e.g., in the left atrium, the right atrium, and the pulmonary vein, in patients with paroxysmal atrial fibrillation or other sustained atrial tachyarrhythmias. The devices include a trapping mechanism for capturing the necrotic tissue debris and may include aspiration capabilities.
Atrial fibrillation is the most common sustained arrhythmia in the United States, affecting over 2 million people. Its prevalence increases with age up to 5 percent in people more than 65 years of age. Atrial fibrillation is perpetuated by reentrant wavelets propagating outside the normal cardiac conduction pathway, resulting in rapid, irregular heart rate and the loss of atrioventricular synchrony. Atrial fibrillation is also important because of the associated fivefold increase in incidence of stroke.
Three patterns of atrial fibrillation exist: paroxysmal (intermittent), persistent (but able to be cardioverted), and permanent (cardioversion-resistent), with the pattern progressing over time in a given patient. Two strategies generally exist for managing patients with atrial fibrillation: rate control and anticoagulation versus attempts to restore and maintain sinus rhythm. Generally, in most patients, initial attempts are undertaken to restore sinus rhythm with electrical or pharmacologic cardioversion. Standard anti-arrhythmic agents include amiodarone, procainamide, or quinidine. However, disadvantages associated with anti-arrhythmic therapy are that (1) the antiarrhythmic agents are pro-arrhythmic, e.g., causing torsades de pointe, (2) the antiarrhythmic agents often carry significant side effects, such as lupus-like syndrome and agranulocytosis, and (3) even with two anti-arrhythmic drugs, some patients may be resistant to pharmacological therapy, e.g., patients may continue to have at least one episode of atrial fibrillation every two days or frequent isolated atrial ectopic beats (more than 700 per day).
If medical therapy fails to convert atrial fibrillation, electrical cardioversion, either externally or via an implanted device, can be attempted using 100 to 200 Wxc2x7s of energy. Anticoagulation is usually recommended to reduce the incidence of embolization associated with cardioversion. Current recommendations suggest long-term anticoagulation for 3 to 4 weeks before cardioversion and 2 to 4 weeks following cardioversion.
Other treatment options for atrial fibrillation include catheter ablation of the atrioventricular (AV) node with pacemaker implantation, or modification of the AV node without pacemaker implantation. However, thromboembolic risk is unchanged and atrial systole is not restored with these procedures. Several alternatives have also been available to interrupt the reentrant wavelets, including extensive surgical, or recently, catheter-medicated atriotomy. Using the current techniques, the success rate of catheter ablation of other sustained atrial arrhythmias, e.g., atrial flutter and sustained atrial tachycardia, has been over 90%. Catheter ablation therefore represents an important alternative to pharmacologic therapy for treatment of atrial fibrillation and other sustained atrial arrhythmias.
In order to ablate the ectopic foci, electrophysiologic study (EPS) is required to locate the foci responsible for triggering of atrial fibrillation. According to Haissaguerre, et al., The New England Journal of Medicine (1998), vol. 339, No. 10, p. 659-666, incorporated herein by reference in its entirety, three multi-electrode catheters are introduced percutaneously through the femoral veins: one catheter for ablation, one mapping catheter for positioning in the right atrial appendage (for locating ectopic foci in the right atrial and right pulmonary vein) or coronary sinus (for locating ectopic foci in the left pulmonary vein), and another catheter for stimulation of the atrial tissue to induce atrial fibrillation. In this study, patients with paroxysmal atrial fibrillation were found to have ectopic beats originating in the atrial muscle (xe2x80x9catrial focixe2x80x9d) and in pulmonary veins (the left superior, left inferior, right superior, and right inferior pulmonary veins). Direct mapping and ablation of the left atrium and pulmonary veins were performed via a transseptal approach through the foramen ovale which lies in the interatrial septum. Alternatively, the catheters may be inserted retrograde in the aorta through the aortic valve and left ventricle. The ablation was performed at the site with earliest recorded ectopic activity.
The ablative techniques used to restore normal sinus rhythm, where the tissue surface is subjected to extreme localized temperature designed to kill cellular structures, can generate necrotic tissue fragments or blood clots. These tissue debris or thrombi may travel downstream from the procedural site to lodge in other organs, causing stroke, myocardial infarction, renal infarcts, and tissue ischemia in other organs. New devices and methods are thus needed for an ablation catheter having an ability to entrap and/or remove embolic debris generated during ablation of ectopic atrial foci in patients with atrial fibrillation or other sustained atrial arrhythmias, thereby reducing the risk of embolization.
It is known that patients with drug and cardioversion refractory paroxysmal atrial fibrillation and other sustained atrial arrhythmias, e.g., atrial flutter and sustained atrial tachycardia, may benefit from catheter ablation of ectopic atrial foci. The present invention provides devices and methods which include filtering and aspiration capabilities for trapping and removing necrotic tissue debris and thrombi generated during the ablative therapy, thereby minimizing embolization to other organs.
In one embodiment, the medical device comprises a catheter which includes a flexible elongate member having a distal end adapted to enter a vessel and a proximal end which extends from a patient""s vessel and permits control outside the patient""s body by a physician. At the distal end of the catheter is provided an ablation device and an expandable trapping mechanism. The ablation device may utilize radio frequency, laser, cryogenic, or microwave. The trapping mechanism, in certain embodiments, comprises an open-ended tubular member which extends to the proximal region of the catheter and is attached to a vacuum. In other embodiments, the trapping mechanism comprises a basket or opening in a tube, which is mounted proximal to the ablation device and surrounds the ablation device.
In another embodiment, the catheter may include a filtration mesh, typically disposed circumferentially about a distal region of the catheter proximal to the ablation device, so that filtration occurs downstream of the ablation. The filter will typically include a continuous mesh having a proximal edge circumferentially in contact with the outer surface of the catheter and a distal edge attached to an expansion mechanism, which contracts and expands radially outward. The construction and use of expansion means and associated filter mesh on a cannula have been thoroughly discussed in our earlier applications, including Barbut et al., U.S. application Ser. No., U.S. application Ser. No. 08/553,137, filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut et al., U.S. Pat. No. 5,769,816, and Barbut et al., U.S. application Ser. No. 08/645,762, filed May 14, 1996, Barbut et al., U.S. Pat. No. 5,662,671, Maahs, U.S. Pat. No. 5,846,260, and Tsugita et al., U.S. Pat. No. 5,911,734, all of which are incorporated herein by reference in their entirety.
In still another embodiment, the catheter includes a second lumen communicating with a proximal end and an aspiration port at its distal end. The proximal end of the catheter is adapted for attachment to a vacuum. The port is located distal to the trapping mechanism and proximal to the ablation device for removing tissue debris generated during the ablation.
In still another embodiment, the device comprises a flexible elongate tube having a lumen communicating with a proximal end and a distal end. An expandable entrapping mechanism is mounted on a distal region of the catheter. An ablation catheter, which includes an ablation device at its distal end, is disposed within the lumen of the catheter. In certain embodiments, the catheter may include a second lumen communicating with a distal port adapted for aspiration of tissue debris.
The methods of the present invention protect a patient from embolization during ablative procedures to remove ectopic atrial foci in the right atrium, the left atrium, and/or the pulmonary veins. Using the devices described above, the distal end of the catheter is inserted percutaneously through a peripheral vein, e.g., the femoral vein, the brachial vein, the subclavian vein, or the internal/external jugular vein, into the right atrium. To ablate the ectopic foci in the right atrial appendage, the ablation device is positioned adjacent to the foci, and the entrapping mechanism, or filter, is expanded. During the ablation, necrotic tissue particles and/or thrombi generated are captured by the filter and/or removed by aspiration. To ablate the ectopic foci in the left atrial tissue or the pulmonary veins, the distal end of the catheter is advanced from the right atrium, through the foramen ovale, and enters the left atrium. Alternatively, the distal end of the catheter may be inserted percutaneously through a peripheral artery, e.g., the femoral artery, the brachial artery, the subclavian artery, or the axillary artery, retrograde into the aorta, the left ventricle, and the left atrium to access the foci in the left atrium or the pulmonary vein. It will be understood that the devices and methods can also be employed in an open surgical procedure (Maze technique).
In another method, after the ectopic atrial foci are located by electrophysiologic mapping, the distal end of the flexible guiding catheter carrying the filter at its distal region is inserted downstream the site of ablation. The filter is expanded. A steerable ablation catheter, having an ablation device mounted at its distal end, is inserted in the lumen of the guiding catheter to ablate the ectopic foci.
After the embolic tissue debris are entrapped by the filter, the filter is contracted to resume a small shape in close contact with the outer surface of the catheter. The catheter, with captured embolic material, is then withdrawn from the aorta or the vein and removed from the patient""s body.
The devices and methods disclosed herein are best used in preventing peripheral embolization during ablation of ectopic foci in the right atrium, the left atrium, and the pulmonary veins in patients with atrial fibrillation or other sustained atrial arrhythmias. It will be understood that the devices and methods are applicable to ablating ectopic tissues in other cardiac arrhythmias, such as ventricular tachycardia or Wolff-Parkinson-White syndrome.